Development of an ex-vivo platform to model immunotherapy in kidney cancer.

592 Background: The treatment landscape for metastatic clear cell renal cell carcinoma (mccRCC) has evolved, with immune checkpoint inhibitor (ICIs) combinations contributing to improved survival. However, many patients remain unresponsive, highlighting the need for alternative strategies. While preclinical models have been instrumental in drug development, their translation to human applications often encounters challenges related to reproducibility. This emphasizes the urgent requirement for accurate, immunocompetent models of ccRCC that reflect human disease, identify effective immunotherapy regimens, and support reliable drug development. This study presents the development and characterization of a precision cut tissue slices (PCTS) model for primary ccRCC, capturing patient-specific heterogeneity. Methods: Twelve patients undergoing nephrectomy for primary ccRCC were consented. PCTS were obtained and co-cultured with autologous peripheral blood mononuclear cells (PBMCs) (5x10^5 co-cultured with one PCTS) and treated for six days. Treatment groups included: i) cabozantinib (cabo) alone, ii) cabo with cemiplimab (cemi, a PD-1 inhibitor), iii) cemi with fianlimab (fin, a LAG-3 inhibitor), and iv) the triplet regimen of cabo, cemi, and fin. The co-cultured PCTS were analyzed using H&E staining and a Live-Dead stain to assess cell viability. Following co-culture, PBMCs were imaged and cytospun for histological analysis and characterized using multiplex immunofluorescence (MxIF). Results: Viability assessment of co-cultured PCTS indicated a significantly higher proportion of dead cells in the triplet-treated group (cabo+cemi+fin) compared with either doublet strategy. Additionally, the number of viable PBMCs, assessed six days post-co-culture, was also highest in the triplet group. Ongoing MxIF analysis aims to characterize the PBMCs further. Conclusions: This study characterizes an organotypic, patient-derived model based on the culture of tumor slices from primary renal cancers, where we have optimized for extended viability of PCTS in ex vivo culture. The drug treatment experiments conducted on the slices demonstrate the potential of PCTS as a preclinical tool for screening effective therapies for primary ccRCC, including immunotherapeutic approaches, which has been challenging in previous animal models. Our findings suggest that the triplet regimen (cabo+cemi+fin) may offer greater efficacy compared to the cabo+cemi or cemi+fin. Based on these results, an early-phase clinical trial to investigate the triplet in ccRCC patients is under development.